RESUMO

It is commonly accepted that plant responses to foliar herbivory (e.g. plant defenses) can influence subsequent leaf-litter decomposability in soil. While several studies have assessed the herbivory-decomposability relationship among different plant species, experimental tests at the intra-specific level are rare, although critical for a mechanistic understanding of how herbivores affect decomposition and its consequences at the ecosystem scale. Using 17 tree species from the Yasuní National Park, Ecuadorian Amazonia, and applying three different herbivore damage treatments, we experimentally tested whether the plant intra-specific responses to herbivory, through changes in leaf quality, affect subsequent leaf-litter decomposition in soil. We found no effects of herbivore damage on the subsequent decomposition of leaf litter within any of the species tested. Our results suggest that leaf traits affecting herbivory are different from those influencing decomposition. Herbivore damage showed much higher intra-specific than inter-specific variability, while we observed the opposite for decomposition. Our findings support the idea that interactions between consumers and their resources are controlled by different factors for the green and the brown food-webs in tropical forests, where herbivory may not necessarily generate any direct positive or negative feedbacks for nutrient cycling.

Assuntos

RESUMO

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) is a tree species found in Brazilian tropical dry forests that retain their leaves during the dry season. That being, we addressed the following question: i) How do insect diversity (sap-sucking and chewing), leaf herbivory and defensive traits (tannin and leaf sclerophylly) vary on the evergreen tree species G. marginata between seasons? The abundance of sap-sucking insects was higher in the dry season than in the rainy season. However, we did not verify any difference in the species richness and abundance of chewing insects between seasons. Leaf herbivory was higher in the rainy season, whereas leaf sclerophylly was higher in the dry season. However, herbivory was not related to sclerophylly. Insect herbivores likely decrease their folivory activity during the dry season due to life history patterns or changes in behaviour, possibly entering diapause or inactivity during this period. Therefore, G. marginata acts as a likely keystone species, serving as a moist refuge for the insect fauna during the dry season in tropical dry forest, and the presence of this evergreen species is crucial to conservation strategies of this threatened ecosystem.

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) é uma árvore encontrada em florestas tropicais secas do Brasil que mantém as suas folhas durante a estação seca. Baseado neste fato, nós levantamos a seguinte questão: i) como a diversidade de insetos herbívoros (sugadores e mastigadores), herbivoria foliar e características defensivas (taninos e esclerofilia foliar) variam em G. marginata entre as estações seca e chuvosa. A abundância de insetos sugadores foi maior na estação seca, entretanto, a riqueza e abundância de insetos mastigadores não diferiram entre as estações. A herbivoria foliar foi maior na estação chuvosa, enquanto a esclerofilia foliar foi maior na estação seca. Não foi observado efeito significativo da esclerofilia sobre os níveis de herbivoria foliar. Insetos herbívoros reduzem a sua atividade de consumo foliar durante a estação seca, fato este devido à sua história natural e/ou mudança comportamental, provavelmente, entrando em diapausa durante este período. Nossos resultados demonstram que G. marginata atua como refúgio para fauna de insetos durante a estação seca, e que a presença desta espécie merece relevante destaque em estratégias de conservação deste ameaçado ecossistema.

Assuntos

RESUMO

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) is a tree species found in Brazilian tropical dry forests that retain their leaves during the dry season. That being, we addressed the following question: i) How do insect diversity (sap-sucking and chewing), leaf herbivory and defensive traits (tannin and leaf sclerophylly) vary on the evergreen tree species G. marginata between seasons? The abundance of sap-sucking insects was higher in the dry season than in the rainy season. However, we did not verify any difference in the species richness and abundance of chewing insects between seasons. Leaf herbivory was higher in the rainy season, whereas leaf sclerophylly was higher in the dry season. However, herbivory was not related to sclerophylly. Insect herbivores likely decrease their folivory activity during the dry season due to life history patterns or changes in behaviour, possibly entering diapause or inactivity during this period. Therefore, G. marginata acts as a likely keystone species, serving as a moist refuge for the insect fauna during the dry season in tropical dry forest, and the presence of this evergreen species is crucial to conservation strategies of this threatened ecosystem.(AU)

Goniorrhachis marginata Taub. (Leguminosae: Caesalpinioideae) é uma árvore encontrada em florestas tropicais secas do Brasil que mantém as suas folhas durante a estação seca. Baseado neste fato, nós levantamos a seguinte questão: i) como a diversidade de insetos herbívoros (sugadores e mastigadores), herbivoria foliar e características defensivas (taninos e esclerofilia foliar) variam em G. marginata entre as estações seca e chuvosa. A abundância de insetos sugadores foi maior na estação seca, entretanto, a riqueza e abundância de insetos mastigadores não diferiram entre as estações. A herbivoria foliar foi maior na estação chuvosa, enquanto a esclerofilia foliar foi maior na estação seca. Não foi observado efeito significativo da esclerofilia sobre os níveis de herbivoria foliar. Insetos herbívoros reduzem a sua atividade de consumo foliar durante a estação seca, fato este devido à sua história natural e/ou mudança comportamental, provavelmente, entrando em diapausa durante este período. Nossos resultados demonstram que G. marginata atua como refúgio para fauna de insetos durante a estação seca, e que a presença desta espécie merece relevante destaque em estratégias de conservação deste ameaçado ecossistema.(AU)

Assuntos

RESUMO

Habitat disturbance alters vegetation structure and composition. For example, in forest fragments, the rate of secondary plant species recruitment and mortality in species typical of old-growth forests are higher. For many arboreal primates, movement between fragments is infrequent and difficult, thus the dietary breadth of herbivorous primates that live in fragments is expected to change. It is likely that the ability of howler monkeys (Alouatta spp.) to live in a large array of habitat types is related to their ability to exploit a broad set of both difficult to digest and high energy resources. However, if small fragments have fewer trees and plant species, food selection by howler monkeys could be limited, which would undermine their persistence. To address this question, we compared the dietary breadth of 14 groups of Yucatán black howler monkeys (Alouatta pigra) living in different fragments, and hypothesized that dietary breadth should be associated to the vegetation attributes of the habitat. We characterized the vegetation structure and composition in each fragment and collected a total of 3,747 focal hr on the feeding behavior of 60 adult individuals. Dietary diversity, both in terms of the rate of plant species used as food sources (plant species used per unit of time) and percentage of ingested food from the top five plant species with overall highest ingestion rate, was not related to vegetation attributes but rather associated with the degree of folivory, such that higher folivory led to more diverse diets. Groups living in fragments with higher tree density used a larger number of trees as food sources. Therefore, black howler monkeys living in small fragments with disturbed vegetation continued to preserve diet diversity, confirming that dietary diversification is an important goal in the foraging strategy of howler monkeys.

Assuntos

RESUMO

The feeding behavior of Artibeus lituratus on leaves of Senna macranthera in an urban area of Uberlandia, Minas Gerais, Brazil, is described, with the first record of folivory by bats on this tree species. Between April and June 1999, direct observations were conducted on the approaching behavior of the bats to bite a leaf, number of bats visiting, time and duration of visits, and intervals between visits. The visits began between 21:00 and 21:15, and finished by 00:00. Each tree was visited simultaneously by up to three bats. Visits lasted on average 8 minutes, with intervals about 20 to 25 minutes. Depending on the position of the leaves, two approaching strategies were used by the bats. Many leaves still connected to tree branches exhibited several bite marks, suggesting that the bats consumed small fragments of leaves and that a leaf could receive more than one visit. Discarded leaf pellets were found beneath a day roost, indicating the use of the liquid portion of the leaves. Aspects of foraging schedule and seasonality of leaf consumption by bats are discussed.

O comportamento de forrageio de Artibeus lituratus sobre folhas de Senna macranthera em uma área urbana do município de Uberlândia, Estado de Minas Gerais, Brasil, é descrito, com o primeiro registro de folivoria por morcegos para esta espécie arbórea. Entre abril e junho de 1999, foram feitas observações diretas do comportamento de aproximação dos morcegos para morder uma folha, número de morcegos visitantes, hora e duração das visitas e intervalo entre as visitas. As visitas iniciaram entre 21:00 e 21:15 e encerraram as 00:00. Cada árvore foi visitada por até três morcegos ao mesmo tempo. As visitas duram em média 8 minutos, com intervalo de 20 a 25 minutos. A aproximação dos morcegos dependeu do posicionamento das folhas, no qual duas formas foram observadas. Várias folhas ainda presas nos galhos exibiam sinais de mordidas, sugerindo que os morcegos consumiam pequenas porções das folhas e que uma folha podia receber mais de uma visita. Pelotas de folhas mastigadas foram encontradas junto a um abrigo diurno, indicando o consumo da parte líquida das folhas. Aspectos do horário de forrageio e do período da estação do ano da folivoria são discutidos.

RESUMO

The feeding behavior of Artibeus lituratus on leaves of Senna macranthera in an urban area of Uberlandia, Minas Gerais, Brazil, is described, with the first record of folivory by bats on this tree species. Between April and June 1999, direct observations were conducted on the approaching behavior of the bats to bite a leaf, number of bats visiting, time and duration of visits, and intervals between visits. The visits began between 21:00 and 21:15, and finished by 00:00. Each tree was visited simultaneously by up to three bats. Visits lasted on average 8 minutes, with intervals about 20 to 25 minutes. Depending on the position of the leaves, two approaching strategies were used by the bats. Many leaves still connected to tree branches exhibited several bite marks, suggesting that the bats consumed small fragments of leaves and that a leaf could receive more than one visit. Discarded leaf pellets were found beneath a day roost, indicating the use of the liquid portion of the leaves. Aspects of foraging schedule and seasonality of leaf consumption by bats are discussed.

O comportamento de forrageio de Artibeus lituratus sobre folhas de Senna macranthera em uma área urbana do município de Uberlândia, Estado de Minas Gerais, Brasil, é descrito, com o primeiro registro de folivoria por morcegos para esta espécie arbórea. Entre abril e junho de 1999, foram feitas observações diretas do comportamento de aproximação dos morcegos para morder uma folha, número de morcegos visitantes, hora e duração das visitas e intervalo entre as visitas. As visitas iniciaram entre 21:00 e 21:15 e encerraram as 00:00. Cada árvore foi visitada por até três morcegos ao mesmo tempo. As visitas duram em média 8 minutos, com intervalo de 20 a 25 minutos. A aproximação dos morcegos dependeu do posicionamento das folhas, no qual duas formas foram observadas. Várias folhas ainda presas nos galhos exibiam sinais de mordidas, sugerindo que os morcegos consumiam pequenas porções das folhas e que uma folha podia receber mais de uma visita. Pelotas de folhas mastigadas foram encontradas junto a um abrigo diurno, indicando o consumo da parte líquida das folhas. Aspectos do horário de forrageio e do período da estação do ano da folivoria são discutidos.

RESUMO

Susceptibility of Didymopanax vinosum (Apiaceae) to insect herbivores was investigated in three sites of a cerrado mosaic - composed of campo cerrado (a grassland with scattered trees and shrubs), cerradão (a tall woodland) and cerrado sensu stricto (intermediate between the two) - situated in Cerrado Pé-de-Gigante, Santa Rita do Passa Quatro, SP, Brazil. We also examined the relationship of folivory with the composition and abundance of the insect herbivore fauna, and with several nutritional and defensive plant characteristics (water, nitrogen, cellulose, lignin, tannin leaf contents, and leaf toughness). We collected insects associated with D. vinosum every month, and we measured leaf damage every three months. In general, the annual folivory differed among sites. It reached the highest rates in site 1 and site 3: 7.33 and 8.5 percent, respectively. Only 1.32 percent of annual folivory was observed in site 2. These levels resulted from the higher abundance, in sites 1 and 3, of the thrips Liothrips didymopanacis (Phlaeothripidae), the most abundant herbivore sampled, responsible for more than 90 percent of the observed damage. However, no significant relationship was found between insect activity and the chemical and physical composition of the leaves. Our findings suggest that, at least in this species, other chemical compounds or variables related to plant apparency and resource availability to herbivores (e.g. plant architecture) might play a more decisive role in the spatial variation of folivory than the nutritional and defensive traits that were analyzed.

A susceptibilidade de Didymopanax vinosum (Apiaceae) a insetos herbívoros foi investigada em três localidades de um mosaico de cerrado - composto de campo cerrado, cerrado sensu stricto e cerradão - localizado no Cerrado Pé-de-Gigante, Santa Rita do Passa Quatro, SP, Brasil. Nosso objetivo foi também relacionar a folivoria com a composição e abundância da fauna de insetos herbívoros, e com várias características nutritivas e defensivas da planta (conteúdo foliar de água, nitrogênio, celulose, lignina, taninos e dureza foliar). Para tanto, coletamos mensalmente os insetos associados a D. vinosum e a cada três meses medimos as injúrias foliares. De modo geral, a herbivoria anual variou entre as localidades. Os maiores valores foram encontrados em plantas da localidade 1 e localidade 3: 7,33 e 8,5 por cento, aproximadamente, contra apenas 1,32 por cento na localidade 2. Esses níveis são resultado da maior abundância, nas localidades 1 e 3, do trips Liothrips didymopanacis (Phlaeothripidae), o principal herbívoro amostrado, responsável por mais de 90% das injúrias observadas. Entretanto, não se encontrou relação entre a atividade desses insetos e a composição química e física das folhas. Nossos resultados indicam que, ao menos para esta espécie, outros compostos químicos ou variáveis relacionadas à aparência e à disponibilidade de recursos aos herbívoros (por exemplo a arquitetura da planta), podem desempenhar um papel mais importante na variação espacial da folivoria que as características nutritivas e as defesas vegetais que foram analisadas.

RESUMO

Susceptibility of Didymopanax vinosum (Apiaceae) to insect herbivores was investigated in three sites of a cerrado mosaic - composed of campo cerrado (a grassland with scattered trees and shrubs), cerradão (a tall woodland) and cerrado sensu stricto (intermediate between the two) - situated in Cerrado Pé-de-Gigante, Santa Rita do Passa Quatro, SP, Brazil. We also examined the relationship of folivory with the composition and abundance of the insect herbivore fauna, and with several nutritional and defensive plant characteristics (water, nitrogen, cellulose, lignin, tannin leaf contents, and leaf toughness). We collected insects associated with D. vinosum every month, and we measured leaf damage every three months. In general, the annual folivory differed among sites. It reached the highest rates in site 1 and site 3: 7.33 and 8.5 percent, respectively. Only 1.32 percent of annual folivory was observed in site 2. These levels resulted from the higher abundance, in sites 1 and 3, of the thrips Liothrips didymopanacis (Phlaeothripidae), the most abundant herbivore sampled, responsible for more than 90 percent of the observed damage. However, no significant relationship was found between insect activity and the chemical and physical composition of the leaves. Our findings suggest that, at least in this species, other chemical compounds or variables related to plant apparency and resource availability to herbivores (e.g. plant architecture) might play a more decisive role in the spatial variation of folivory than the nutritional and defensive traits that were analyzed.

A susceptibilidade de Didymopanax vinosum (Apiaceae) a insetos herbívoros foi investigada em três localidades de um mosaico de cerrado - composto de campo cerrado, cerrado sensu stricto e cerradão - localizado no Cerrado Pé-de-Gigante, Santa Rita do Passa Quatro, SP, Brasil. Nosso objetivo foi também relacionar a folivoria com a composição e abundância da fauna de insetos herbívoros, e com várias características nutritivas e defensivas da planta (conteúdo foliar de água, nitrogênio, celulose, lignina, taninos e dureza foliar). Para tanto, coletamos mensalmente os insetos associados a D. vinosum e a cada três meses medimos as injúrias foliares. De modo geral, a herbivoria anual variou entre as localidades. Os maiores valores foram encontrados em plantas da localidade 1 e localidade 3: 7,33 e 8,5 por cento, aproximadamente, contra apenas 1,32 por cento na localidade 2. Esses níveis são resultado da maior abundância, nas localidades 1 e 3, do trips Liothrips didymopanacis (Phlaeothripidae), o principal herbívoro amostrado, responsável por mais de 90% das injúrias observadas. Entretanto, não se encontrou relação entre a atividade desses insetos e a composição química e física das folhas. Nossos resultados indicam que, ao menos para esta espécie, outros compostos químicos ou variáveis relacionadas à aparência e à disponibilidade de recursos aos herbívoros (por exemplo a arquitetura da planta), podem desempenhar um papel mais importante na variação espacial da folivoria que as características nutritivas e as defesas vegetais que foram analisadas.